The overall objective of the proposed project is to augment an on- going-but still in the design phase-projected longitudinal study of children and youth (age "cohorts" of 7, 9, 11, 13, and 15 years of age) with a research component that focuses directly on drug use. The specific objectives include 1) to more adequately examine the developmental process and factors surrounding initiation into drug use and factors associated with the prevention of initial drug use; 2) a focused examination of the role of peers and friendships in drug use initiation, maintenance, escalation, and termination; 3) to provide incidence and prevalence of types and patterns (combinations) of drug use in high risk minority and anglo groups and to obtain information about sources of drugs, amounts used, mode of administration, and social and physical setting of use; 4) to examine the factors surrounding the etiology of drug use and to test the ability of an integrated theory to explain initiation, maintenance, and termination of drug use; and 5) to examine the consequences of drug use for family interactions, school attendance and performance, behavioral problems and delinquency, and other drug related problem behavior. The sample of the proposed study is a probability sample of 1500 children and adolescents drawn from "high risk" delinquency and drug use neighborhoods of Denver, Colorado. A much larger probability sample of youth from these neighborhoods will be initially screened for risk and a disproportionate number of high risk cases included in the study sample. The combination of longitudinal measures of drug use and delinquency, personal beliefs and attitudes, demographic and neighborhood characteristics, and peer, family, school and medical history influences, all from one probability sample, should permit a number of important issues to be addressed by the proposed project.